[Issue 7154] New: [CTFE] failing downcast causes error

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=7154

           Summary: [CTFE] failing downcast causes error
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: maehlvis at googlemail.com


--- Comment #0 from Elvis Maehren <maehlvis at googlemail.com> 2011-12-22 07:45:40 PST ---
At runtime, a failing downcast evaluates to null.
At compile time, it gives an error:
"Error: cannot reinterpret class from C to test.B at compile time"
It should just evaluate to null, too.

---
class A {}
class B : A {}
class C : A {}

bool test(T)() {
    A a = new T;
    return (cast(B) a) !is null;
}

void main() {
    assert(test!B()); // ok
    assert(!test!C()); // ok
    static assert(test!B()); // ok
    static assert(!test!C()); // error
}
---

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